Re: [PATCH 6/8] drm/msm/dp: Add maximum width limitation for modes

[Xiangxu Yin <quic_xiangxuy@xxxxxxxxxxx>]

On 11/29/2024 9:52 PM, Dmitry Baryshkov wrote:
> On Fri, 29 Nov 2024 at 09:59, Xiangxu Yin <quic_xiangxuy@xxxxxxxxxxx> wrote:
>>
>> Introduce a maximum width constraint for modes during validation. This
>> ensures that the modes are filtered based on hardware capabilities,
>> specifically addressing the line buffer limitations of individual pipes.
> 
> This doesn't describe, why this is necessary. What does "buffer
> limitations of individual pipes" mean?
> If the platforms have hw capabilities like being unable to support 8k
> or 10k, it should go to platform data
> 
It's SSPP line buffer limitation for this platform and only support to 2160 mode width.
Then, shall I add max_width config to struct msm_dp_desc in next patch? for other platform will set defualt value to ‘DP_MAX_WIDTH 7680'
>>
>> Signed-off-by: Xiangxu Yin <quic_xiangxuy@xxxxxxxxxxx>
>> ---
>>  drivers/gpu/drm/msm/dp/dp_display.c |  3 +++
>>  drivers/gpu/drm/msm/dp/dp_display.h |  1 +
>>  drivers/gpu/drm/msm/dp/dp_panel.c   | 13 +++++++++++++
>>  drivers/gpu/drm/msm/dp/dp_panel.h   |  1 +
>>  4 files changed, 18 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
>> index 4c83402fc7e0d41cb7621fa2efda043269d0a608..eb6fb76c68e505fafbec563440e9784f51e1894b 100644
>> --- a/drivers/gpu/drm/msm/dp/dp_display.c
>> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
>> @@ -944,6 +944,9 @@ enum drm_mode_status msm_dp_bridge_mode_valid(struct drm_bridge *bridge,
>>         msm_dp_display = container_of(dp, struct msm_dp_display_private, msm_dp_display);
>>         link_info = &msm_dp_display->panel->link_info;
>>
>> +       if (mode->hdisplay > msm_dp_display->panel->max_dp_width)
>> +               return MODE_BAD;
>> +
>>         if (drm_mode_is_420_only(&dp->connector->display_info, mode) &&
>>             msm_dp_display->panel->vsc_sdp_supported)
>>                 mode_pclk_khz /= 2;
>> diff --git a/drivers/gpu/drm/msm/dp/dp_display.h b/drivers/gpu/drm/msm/dp/dp_display.h
>> index ecbc2d92f546a346ee53adcf1b060933e4f54317..7a11f7eeb691976f06afc7aff67650397d7deb90 100644
>> --- a/drivers/gpu/drm/msm/dp/dp_display.h
>> +++ b/drivers/gpu/drm/msm/dp/dp_display.h
>> @@ -11,6 +11,7 @@
>>  #include "disp/msm_disp_snapshot.h"
>>
>>  #define DP_MAX_PIXEL_CLK_KHZ   675000
>> +#define DP_MAX_WIDTH   7680
>>
>>  struct msm_dp {
>>         struct drm_device *drm_dev;
>> diff --git a/drivers/gpu/drm/msm/dp/dp_panel.c b/drivers/gpu/drm/msm/dp/dp_panel.c
>> index 8654180aa259234bbd41f4f88c13c485f9791b1d..10501e301c5e073d8d34093b86a15d72e646a01f 100644
>> --- a/drivers/gpu/drm/msm/dp/dp_panel.c
>> +++ b/drivers/gpu/drm/msm/dp/dp_panel.c
>> @@ -4,6 +4,7 @@
>>   */
>>
>>  #include "dp_panel.h"
>> +#include "dp_display.h"
>>  #include "dp_utils.h"
>>
>>  #include <drm/drm_connector.h>
>> @@ -455,6 +456,16 @@ static u32 msm_dp_panel_link_frequencies(struct device_node *of_node)
>>         return frequency;
>>  }
>>
>> +static u32 msm_dp_panel_max_width(struct device_node *of_node)
>> +{
>> +       u32 max_width = 0;
>> +
>> +       if (of_property_read_u32(of_node, "max-width", &max_width))
>> +               max_width = DP_MAX_WIDTH;
>> +
>> +       return max_width;
> 
> msm_dp_panel->max_dp_width = DP_MAX_WIDTH;
> of_property_read_u32(of_node, "max-width", &msm_dp_panel->max_dp_width);
> 
>> +}
>> +
>>  static int msm_dp_panel_parse_dt(struct msm_dp_panel *msm_dp_panel)
>>  {
>>         struct msm_dp_panel_private *panel;
>> @@ -490,6 +501,8 @@ static int msm_dp_panel_parse_dt(struct msm_dp_panel *msm_dp_panel)
>>         if (!msm_dp_panel->max_dp_link_rate)
>>                 msm_dp_panel->max_dp_link_rate = DP_LINK_RATE_HBR2;
>>
>> +       msm_dp_panel->max_dp_width = msm_dp_panel_max_width(of_node);
>> +
>>         return 0;
>>  }
>>
>> diff --git a/drivers/gpu/drm/msm/dp/dp_panel.h b/drivers/gpu/drm/msm/dp/dp_panel.h
>> index 7603b92c32902bd3d4485539bd6308537ff75a2c..61513644161209c243bbb623ee4ded951b2a0597 100644
>> --- a/drivers/gpu/drm/msm/dp/dp_panel.h
>> +++ b/drivers/gpu/drm/msm/dp/dp_panel.h
>> @@ -51,6 +51,7 @@ struct msm_dp_panel {
>>         u32 lane_map[DP_MAX_NUM_DP_LANES];
>>         u32 max_dp_lanes;
>>         u32 max_dp_link_rate;
>> +       u32 max_dp_width;
>>
>>         u32 max_bw_code;
>>  };
>>
>> --
>> 2.25.1
>>
> 
>